Improving the Diagnosis and Treatment of Urinary Tract Infection in Young Children in Primary Care: Results from the DUTY Prospective Diagnostic Cohort Study

The DUTY study's recent publication in the Annals of Family Medicine on 'improving the diagnosis and treatment of urinary tract infection (UTI) in young children in primary care' gives the impression of describing a typical cross-section of 'acutely unwell children aged under 5 years' who might be seen in general practice across England and Wales [1]. Since childhood UTI management guidelines focus on infants aged <2 years [2, 3] who are especially difficult to diagnose, and most likely to acquiring renal scarring, it is likely that most readers will assume that this vulnerable group are well represented within the DUTY cohort. They would be very wrong, though it is necessary to review the results section in detail, and to use a calculator to appreciate this.

Instead, they have only reported on 2,740 (54.6%) of the 5,017 eligible cases that they enrolled according to their study plan, and >70% of these are over 3 years old (no mean, standard deviation, median or range provided). This is because the DUTY team decided post-study to exclude the 92.7% of the infants who were (a) aged <2 years, and/or (b) still in nappies, because their urine samples were collected using nappy pads, which they later concluded were 'less accurate and more often contaminated' than clean-catch specimens [4]. However, that conclusion was incorrectly reached from the evidence they had obtained. Instead of comparing the contamination rates of nappy pad and clean-catch collections in infants of a similar age, they compared pad urines from non-continent infants with a mean age of 1.3 years (standard error 0.017) with clean- catch specimens from children with an average age 3.5 years (standard error 0.019), which are highly significantly different age-groups (p<0.00001, unpaired t-test). A difference in contamination rates would be almost inevitable between children in these age-groups using the same collection method [2, 3], and cannot be assumed to be due to sampling technique.

In summary, the DUTY paper describes children mainly between 3 and 5 years old, and hugely under-represents infants aged <2 years who are the most vulnerable, because of incorrect conclusions drawn from flawed data analysis. I was the paediatric nephrology member of the DUTY Scientific Steering Committee until 2013, but resigned after expressing fundamental concerns about the study's scientific quality to that committee, and to the National Institute for Health Research (NIHR) who were funding it. I am disappointed to find that some of the data has been published containing inappropriate data analysis, which has led to misleading conclusions and unjustified recommendations.

References

1. Hay AD, Sterne JAC, Hood K, Little P, Delaney B, Hollingsworth W, et al. Improving the diagnosis and treatment of urinary tract infection in young children in primary care: results from the DUTY prospective diagnosis cohort study. Ann Fam Med 2016;14:325-36.

2. National Institute for Health and Clinical Excellence (NICE). Urinary tract infection in children. (http://guidance.nice.org.uk/CG054) 2007.

3. American Academy of Pediatrics. Urinary tract infection: Clinical practice guideline for the diagnosis and management of the initial UTI in febrile infants and children 2 to 24 months. Pediatr 2011;128:595-610.

4. Butler CC, Sterne JAC, Lawton M, O'Brien K, Wootton M, Hood K, et al. Nappy pad urine samples for investigation and treatment of UTI in young children: the DUTY prospective diagnostic cohort study. Br J Gen Pract 2016;DOI:10.3399/bjgp16X685873 (abridged text in print;Br J Gen Pract 2016;66:367-368).

Competing interests: I am one of the authors who first suggested the use of 'Newcastle nappy pads'.